Dope Sheet keyframes: shear keyframes
Assuming the lamps are sortable by their name and the animation (which is supposed to be shifted) is the only animation on the object, the you could use a python script to shift the keyframes of all fcurves of an object.

To use the script, selected the objects and execute the script. The selected objects must have an existing animation. First make sure to make the materials single user, by selecting all objects, then pressing U in the 3D View and choosing Material and Texture.

By changing the value of the offset_amount variable, you can change the timing.
Decimal values 0 &lt; x &lt; 1 are also possible.

import bpy

offset_amount = 2.0

# get selected objects
sel = bpy.context.selected_objects

# sort them by name
sel.sort(key=lambda x: x.name)



# loop through all selected objects
for i, s in enumerate(sel):
    # get the fcurves of the active action
    # of the material of the object

    fcurves = s.material_slots[0].material.node_tree.animation_data.action.fcurves

    # loop through all fcurves
    for fc in fcurves:
        # loop through all keyframes
        for kp in fc.keyframe_points:
            # change the x (time) value of the keyframe
            kp.co.x += offset_amount * i